Fix skipped slot detection for eager rent collect (#10890)

runtime/src/bank.rs

@@ -1875,21 +1875,6 @@ impl Bank {
         let (parent_epoch, mut parent_slot_index) =
             self.get_epoch_and_slot_index(self.parent_slot());
 
-        let mut partitions = vec![];
-        if parent_epoch < current_epoch {
-            if current_slot_index > 0 {
-                // Generate special partitions because there are skipped slots
-                // exactly at the epoch transition.
-
-                let parent_last_slot_index = self.get_slots_in_epoch(parent_epoch) - 1;
-
-                // ... for parent epoch
-                partitions.push(self.partition_from_slot_indexes_with_gapped_epochs(
-                    parent_slot_index,
-                    parent_last_slot_index,
-                    parent_epoch,
-                ));
-
         let should_enable = match self.operating_mode() {
             OperatingMode::Development => true,
             OperatingMode::Preview => current_epoch >= Epoch::max_value(),
@@ -1905,9 +1890,32 @@ impl Bank {
                 should_enable
             }
         };
+
+        let mut partitions = vec![];
+        if parent_epoch < current_epoch {
             // this needs to be gated because this potentially can change the behavior
             // (= bank hash) at each start of epochs
-                if should_enable {
+            let slot_skipped = if should_enable {
+                (self.slot() - self.parent_slot()) > 1
+            } else {
+                current_slot_index > 0
+            };
+            if slot_skipped {
+                // Generate special partitions because there are skipped slots
+                // exactly at the epoch transition.
+
+                let parent_last_slot_index = self.get_slots_in_epoch(parent_epoch) - 1;
+
+                // ... for parent epoch
+                partitions.push(self.partition_from_slot_indexes_with_gapped_epochs(
+                    parent_slot_index,
+                    parent_last_slot_index,
+                    parent_epoch,
+                ));
+
+                // this needs to be gated because this potentially can change the behavior
+                // (= bank hash) at each start of epochs
+                if should_enable && current_slot_index > 0 {
                     // ... for current epoch
                     partitions.push(self.partition_from_slot_indexes_with_gapped_epochs(
                         0,
@@ -3642,7 +3650,7 @@ mod tests {
     }
 
     #[test]
-    fn test_rent_eager_across_epoch_with_gap() {
+    fn test_rent_eager_across_epoch_with_full_gap() {
         let (genesis_config, _mint_keypair) = create_genesis_config(1);
 
         let mut bank = Arc::new(Bank::new(&genesis_config));
@@ -3659,6 +3667,30 @@ mod tests {
             bank.rent_collection_partitions(),
             vec![(14, 31, 32), (0, 0, 64), (0, 17, 64)]
         );
+        bank = Arc::new(new_from_parent(&bank));
+        assert_eq!(bank.rent_collection_partitions(), vec![(17, 18, 64)]);
+    }
+
+    #[test]
+    fn test_rent_eager_across_epoch_with_half_gap() {
+        let (genesis_config, _mint_keypair) = create_genesis_config(1);
+
+        let mut bank = Arc::new(Bank::new(&genesis_config));
+        assert_eq!(bank.rent_collection_partitions(), vec![(0, 0, 32)]);
+
+        bank = Arc::new(new_from_parent(&bank));
+        assert_eq!(bank.rent_collection_partitions(), vec![(0, 1, 32)]);
+        for _ in 2..15 {
+            bank = Arc::new(new_from_parent(&bank));
+        }
+        assert_eq!(bank.rent_collection_partitions(), vec![(13, 14, 32)]);
+        bank = Arc::new(Bank::new_from_parent(&bank, &Pubkey::default(), 32));
+        assert_eq!(
+            bank.rent_collection_partitions(),
+            vec![(14, 31, 32), (0, 0, 64)]
+        );
+        bank = Arc::new(new_from_parent(&bank));
+        assert_eq!(bank.rent_collection_partitions(), vec![(0, 1, 64)]);
     }
 
     #[test]